If a person keeps Discus and....?

...does around 50% water changes every day or every couple days, then they do not have a aquarium with enough bacteria to support the fish, right? By doing that many water changes to keep levels perfect for the Discus, they are also getting rid of the bacteria.

So, if they did a 50% water change one day and did not do another water change until the next week, the levels would be raising causing the tank to go into a mini cycle? But since they do big water changes often to keep ammonia and nitrite levels perfect, they do not really have to worry about mini cycles or raising levels?

Am I correct?

I have always admired people who keep discus, they do so much work :P


Most beneficial bacteria are in the filter.

Constant water changes like that are not always necessary. For breeding or rapidly growing fish they might be necessary, but Water Volume is the best way to get a more stable tank if we're just talking display tank. Discus keepers may be slightly insane.

One issue with discus, is if the tank Ph is kept low, the normal bacterial filtration doesn't function as well. Ammonia is not reduced as effectively at lower Ph. The water changes might be necessary if filtration or water volume was not enough to do it on it's own. .

yes, conceivably the water changes could avoid a cycle, but like you noticed, an interruption might cause the ammonia level to shoot up, because the filter wasn't properly developed with enough bacteria to handle the daily ammonia production. This could happen any time, not only in the first few months.

the breeder I worked for had no filters except for two sponge filters in every tank, except for the discus which also had a biowheel filter. Every tank was on a constant drip, drip , drip of new water 24/7 . Some were 40 gallon tanks with hundreds of fry and handfuls of food going in three times a day. Waste was vacuumed out every week or so in tanks that needed it, but primarily it was the constant water change that made it possible to break most of the "rules". (note, he did not soften the water and ours is very hard/with high Ph. He successfully bred angels , rainbows, discus etc. in this water)

I think, having a larger water volume, by adding a large sump or tank to the system, would be better than the daily water changes you often hear about. Aging the water used for water changes, would be helpful as well.


Large water changes are needed with some juvi discus so they develop normally. The bacteria does not live in the water column, so large frequent water changes do not hurt the cycle at all. The cleaner the water the better for all fish. I change 50% at least once a week in all of my tanks. But doing it daily won't hurt either.